Apparatus for the application of injection pressure in pressure casting machines



Dec. 5, 1939.

w. H. SCHWARTZ l 2,182,059 APPARATUS FOR THE APPLICATION 0F INJECTION PRESSURE IN PRESSURE CASTING MACHINES Filed Dec. 2, 1957 AT. mxEYS Patented Dec. 5, 1939,

APPARATUS FOR THE APPLICATION F IN- JECTION PRESSURE IN PRESSURE CAST- ING MACHINES William H. Schwartz, Cleveland, Ohio, assignor -to Lester Engineering Company, Cleveland,

Ohio, a corporation of Ohio Application December 2. 1937, Serial No. 177,723 I Claims. (Cl. 22-68) 'I'he present invention relates to pressure casting machines and has particular reference to apparatus for automatically controlling the rate of, sequence of, and amount of prime moving 5 pressure. applied to operate the material injection or pressure casting mechanism of such a machine. My invention is applicable to pressure casting machines used for both metallic and nonmetallic materials, such as non-ferrous metals and alloys, and plastics, respectively.

The general object and nature of my invention is to so vcontrol the prime moving pressure applied to the injection cylinder of a pressure casting machine that there will result a hammer blow eifect during the final portion of the casting stroke of the injection mechanism.

In pressure casting, thereis a tendency of the material to be cast to solidify or partially freeze out, or to offer greater resistance to movement through theinjection mechanism and into the mold or die cavity during such time as the material is nearing a complete occupation or filling of the mold. In the pressure casting of plastic materials especially, it is necessary that the material to be cast be moved at first slowly through the injection passages wherein it is subjected to heating, and be moved finally at a greatly increased rate into the mold. My invention, therefore, provides a process and apparatus for building up .or accumulating excess pressure and then automatically applying this excess pressure to the injection mechanism, as the piston of the injection cylinder approaches the end of its pressure casting stroke.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of various ways in which the principle of the invention may be used.

In said annexed drawing:

The single figure of the annexed drawing is a more or less diagrammatic representation of an apparatus embodying the principle of my invention.

Now referring more particularly to the drawing, there is shown therein an injection cylinder I in which a piston 2 mounted upon the piston rod 3 is adapted to reciprocate. The piston rod 3 of course will be connected to the material casting cylinder (not shown) of a pressure casting machine. A conduit 4 from the head end of the cylinder I and a conduit 5 from the rod end of the cylinder I lead to a four-way valve 6, such as is customarily employed in the installation of pressure casting machines.

A conduit 1 places the four-way valve 5in com- B muncation with the pressure pump 8. The pressure pump 8 receives a iiuid pressure medium such as oil from the reservoir 9, and is driven by an electric motor I0. The customary drain line II also leads from the four-Way valve 6 to the 10 reservoir 9. A pressure storage chamber onaccumulator I2 is connected to the pressure supply line 1 by means of the conduit I3. The accumulator I2 is adapted to contain air or a gas such as nitrogen and to receive excess pressure 15 delivered from the supply line 1.

A check valve I4 is located in the supply line 1 and a check valve I5 is located in the line I3. The check valves I44 and I5 are so disposed that they will permit ilow only in a direction away 20 from the pressure pump 8.

A secondary or by-pass conduit or line I8 leads from the accumulator I 2 to the supply line 1 at a point beyond .the check valve I4. Flow through the line I6 is controlled by the pilot valve 25 f I1. The pilot valve I1 in turn is actuated by means of pressure introduced through the line I8 to one end of its valve element I9. 'I'he opposite end of the valve element I9 is mounted against the compression spring 20 which in turn 30 is adjustable as to compression by means of the set screw 2l.

'I'he operation of the above-described apparatus is as follows: Assuming that the injection cylinder piston 2 is ready to begin its casting 35 stroke, or in the position as indicated in the drawing, the four-way valve 6 will be so operated as to direct pressure from the pump 8, through the line 1 through the line 4 to the head end of the cylinder I. Assuming that for'a given in- 40 stallation a pressure of 250 pounds per square inch will be suiiicient to move the injection cylinder piston through the rst and major portion of its stroke, the latter will travel on such stroke until resistance is met due to the lling of the 45 pressure casting machine mold cavity, or due to the partial solidification or freezing out of the material. At this point, due to the factv that the iluid in the cylinder I and in the lines 4 and 1 cannot expand and is restricted to volume, back 50 pressure will be built up and communicated through the line I8to the pilot valve I1. Dependent upon the pressure adjustment setting of the pilot valve I1. the latter will be operated to place the excess pressure stored in the accumu- 55 lator I2 in communication, through the line I6, through the valve 6, and through the line 4 with the cylinder I. Assuming that the accumulated pressure in the accumulator I2 is 1000 pounds per square inch, it will thus be seenthat a sudden increase in pressure, having the eifect of a hammer blow is delivered to the injection cylinder I to nally drive the latter home.

In the next cycle of operation, the four-way valve 6 is so operated as to return the injection cylinder piston 2 to its original position, by releasing the pressure in the line 4 and applying pressure from the line 1 tothe line 5. As pressure in the line 4 is decreased, the pilot valve I 1 is permitted to return to its oif position, as illustrated in the ldrawing and to thus close the bypass line I 6. As the injection cylinder piston 2l reaches its return position, it is caused to dwell there for a certain period of time, while other parts of the pressure casting machine are being operated, such as the opening and closing of the dies and the feeding of the material to the mechanism. During this period, the line 1 is closed olf by the valve 6, with the result that a back pressure is built up in the -Iine 1 and communicated-l through the line I3, the check valve I5, to the accumulator I2, thus replenishing the supply of excess pressure, rendering it available for the next cycle of operations, or the next injection shoth j.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated -by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a pressure casting machine, having means for injecting material in the die cavity of said machine, a pressure supply source connected to said material injecting means for operating the latter during the first portion of its stroke, and a second pressure supply source, the combination of pressure responsive means actuated by the operating pressure of said material injecting means for connecting said second pressure supply source to said material injecting means during the nnal portion of its stroke, and means for adjustably regulating the pressure at which said pressure responsive means is actuated. l l

2. In apressure casting machine, having means Ai'or injecting materialin the die cavity ol.' said machine, va pressure` supply source connected to said material injecting means, and a pressure storage means connected to said pressure supply source, the combination of valve means for con necting said pressure storage means to said material injecting means, said valve means being l0 actuated by the pressure delivered to said material injecting means from said pressure supply source, and means for adjustably regulating the pressure at which said valve means is actuated.

3. In a pressure casting machine, the comll bination of means for injecting material in the die cavity lof said machine, a pressure supply source, and a pressure storage means, the combination of valve means for intermittently connecting said pressure supply source to said material injecting means,` one-way valve means constantly connecting said lpressure storage means to said pressure supply source, and a ,l

third valve means for connecting said pressure storage means to said material injecting means when the pressure delivered to said material injecting means exceeds a predetermined amount.

4. In a pressure casting machine, the combination of an injection cylinder, a. pressure pump,

lan intermittently operated valve connecting said '3.0

pump to said cylinder, a pressure storage tank,

a check valve connecting said tank to said pump,. said check valve preventing flow from said tank to said pump and a pilot valve connecting said tank to said cylinder, said pilot valve being actuated by pressure in said cylinder.

5. In a pressure casting machine having means for injecting material ,in the die cavity of said machine, a pressure supply source connected to said material injecting means, the combination of a pressure ,storage means connected to said` pressure supply source, and valve means ,for connecting said pressure storage means to said material injecting means, said valve' means being actuated by the pressure delivered to said ma- 4.5 terial injecting means from said pressure supply Source.

WILLIAM H. SCHWARTZ. 

